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BiologyThe black-crowned night heron is an opportunistic predator, with a varied diet that includes small fish, crabs, crayfish, snakes, amphibians, small rodents, the chicks of other birds, insects and sometimes plant matter (2) (4) (6). Although a gregarious species, individuals generally forage alone, feeding throughout the night from dusk to early morning (2) (3). In the dimly lit hours of night, prey is pinpointed with the help of exceptional eyesight, and retrieved with a swift grasp of the bill (3). However, during the breeding season, when food is in high demand, daytime foraging is also relatively common (2) (4) Nesting occurs in large colonies, often comprising several different species, and located on islands or other suitable sites where predators pose less of a threat (2). During the breeding season, the male establishes a territory and typically performs a variety of displays to attract a female, including exaggerated bows that accentuate the white neck plumes, bill snapping, and twig shaking (2) (6). Initially the male constructs the nest alone, but following pair formation, the male presents twigs to the female, who in turn works them into the nest. The shallow nest may be located in the branch of a tree or shrub, in a reed bed or even just on the ground (2). Following copulation the female lays three to five greenish eggs, which are incubated by both parent birds for 24 to 26 days before hatching. The young are fed on food regurgitated by the parent birds and fledge after six to seven weeks, sometimes forming small flocks, and may continue to beg for food from the adults (6). Northern populations of the black-crowned night heron are migratory, travelling south over winter after the breeding season. Conversely, tropical populations, which nest during the rainy season, are largely sedentary, but may also exhibit some dispersal movements post-breeding (4).